Radiometric Dating of Mississippi Valley-type Ore Deposits Utilizing U-Pb and Th-Pb for Hydrothermal Calcite and Rb-Sr for Sphalerite

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9614264 Brannon The proposed work seeks to improve on the isotopic methodology for dating ore-stage mineralization in Mississipi Valley-type (MVT) Pb-Zn deposits in order to provide necessary constraints for understanding the mechanisms of ore formation. The proposed study will concentrate on: (1) the radiometric dating of two North American MVT ore deposits (Illinois-Kentucky-Fluorspar and Pine-Point Zn-Pb deposits) for which conflicting ages of ore formation exist at the moment; (2) dating of ore-stage calcite and sphalerite from mines of the Tri-State (Missouri, Kansas, Oklahoma) MVT district; and (3) dating two Proterozoic MVT deposits in South Africa, thought to be among the oldest deposits of this type currently known. In addition to dating, the Rb-Sr and U-Th-Pb isotopic systematics will be used as tracers of the ore-forming fluids. Information on the source of fluids is necessary to assess models of ore genesis in the various localities and to construct a better genetic model for MVT's worldwide.